1. Field of the Invention
This invention relates to a safety device suitable for an electrical power window apparatus, more particularly to an anti-pinching function of the power window apparatus.
2. Description of the Related Art
An anti-pinching- function is indispensable for power window apparatus in order to avoid risk of an serious accident to pinch human bodies between a window glass and a sash. In order to achieve this function, it is well known to detect human bodies inserted between the window glass and the sash, and stop or rotate in reverse the window regulator motor to keep the window glass from the detected human bodies. In order to the detection, four types of inventive technologies are already proposed.
First type of those technologies detects mechanical overload of the window regulator motor. In this type, the mechanical overload is detected by monitoring electrical overload of the motor drive current. An embodiment of the first type is disclosed in Japanese Patent Laid Open No. Hei 6-335284 for instance.
Second type of those technologies also detects mechanical overload. However, in this type, the mechanical overload is detected by monitoring not electrical overload but drive current pulse disorder of the regulator motor. An embodiment of the second type is disclosed in Japanese Patent Laid Open No. Hei 5-321530 for instance.
Third type of those technologies detects human bodies directly. In this type, a capacitor is elongated along the sash, and its capacitance is monitored by a monitoring circuit when the regulator motor is activated. In case human bodies are pinched between the window glass and the sash, the capacitor alters its capacitance caused by human bodies' capacitance, and the monitoring circuit detects that a pinching accident has occurred. An embodiment of the third type is disclosed in Japanese Utility model Laid Open No. Sho 61-104221 for instance.
And the fourth type of those technologies also detects human bodies directly. However, in this type, elongated along the sash is not a capacitor but a touch sensor. In case human bodies are pinched between the window glass and the sash, this touch sensor detects pressure despite the edge of the window glass does not reach the touch sensor yet. An embodiment of the fourth type is disclosed in Japanese Patent Laid Open No. Sho 60-119883 for instance.
Accordingly, the first type and the second type inevitably bring pain for the pinched human bodies. This pain is a result of the mechanical overload. So, the pain is unavoidable even if sensitivity of the detection is progressed. In addition, electrical property of the parts should be regulated to avoid ignorance or over-detection of human bodies. This regulation should be provided by each products to compensate variation of the parts, such as motor torque, sensor sensitivity, or occilate frequency. This regulation will bring serious disadvantage in productivity or cost because the regulation process consumes considerable labor.
Additionally in the third type, it is technically complicated to insert conductive terminal in the window glass edge to produce capacitor sensor, or
it is also complicated or difficult to compensate change of the parts according to time passage, such as capacity drift.
Or in the fourth type, conductive terminals shall be provided at the window glass edge by baking, then a pressure-sensitive conductive rubber seat shall be sticked on the conductive terminals, and the surface of the pressure-sensitive conductive rubber seat shall be coated with sericone rubber. Accordingly, those structure or production process will be unavoidably become complicated, and glass coating print circuit will be indispensable to connect the capacitor terminals with other electrical circuit parts of the power window system.